WO2015052838A1

WO2015052838A1 - Decoupling circuit

Info

Publication number: WO2015052838A1
Application number: PCT/JP2013/077792
Authority: WO
Inventors: 英俊牧村; 西本　研悟; 深沢　徹; 良和吉田; 和宜大塚
Original assignee: 三菱電機株式会社
Priority date: 2013-10-11
Filing date: 2013-10-11
Publication date: 2015-04-16
Also published as: JPWO2015052838A1

Abstract

A decoupling circuit is configured such that signal distribution ratios in distribution circuits (1, 2) and an amplitude adjustment amount in an amplitude phase adjustment circuit (5) are set such that coupling amplitudes in a route A and a route B become equal and a phase adjustment amount in the amplitude phase adjustment circuit (5) is set such that coupling phases in the route A and the route B become opposite to each other. Consequently, even if the coupling amplitude and coupling phase between antennas greatly change in a usable frequency band, the coupling between an input/output terminal (11) and an input/output terminal (21) can be reduced over the whole usable frequency band.

Description

Decoupling circuit

The present invention relates to, for example, a decoupling circuit that connects a plurality of antennas mounted on a wireless communication device or the like, and more particularly, to a decoupling circuit that reduces coupling between two antennas.

In recent years, with the increase in speed and quality of wireless communication systems, there is an increasing demand for multi-antenna technology using a plurality of antennas in order to apply diversity and MIMO (Multiple Input Multiple Output).
In order for diversity and MIMO to exhibit sufficient effects, it is necessary to reduce the coupling between a plurality of antennas as much as possible to lower the antenna correlation.

However, in general, when multiple antennas are mounted in a small area such as a small communication terminal, the distance between the antennas cannot be sufficiently secured, so that the coupling between the antennas is increased and the communication performance is increased. May deteriorate.
As a method for avoiding the problem of strong coupling between antennas, a method is known in which a decoupling circuit is connected between a plurality of antennas, and the coupling between antennas via a space is canceled by the decoupling circuit.

For example, the following Non-Patent Document 1 discloses a decoupling circuit composed of two transmission lines and a reactance element that connects the two transmission lines. The mutual coupling is reduced.
The following Patent Document 1 discloses a method of reducing coupling between antennas by connecting antennas with a connection circuit.

JP 2012-227742 A

Since the conventional decoupling circuit is configured as described above, in principle, the coupling is reduced at one frequency. For this reason, when the frequency band to be used is wide, there existed a subject which cannot reduce coupling in the whole use frequency band.
In particular, when the coupling phase between the antennas greatly changes within the used frequency band, there is a problem that the coupling cannot be reduced over the entire used frequency band.

The present invention has been made to solve the above-described problems, and provides a decoupling circuit capable of reducing the coupling in the entire used frequency band even when the coupling phase greatly changes in the used frequency band. For the purpose.

The decoupling circuit according to the present invention has a first signal distribution means for distributing a signal input from the first input / output terminal to the second and third input / output terminals, and a signal input from the fourth input / output terminal. The second signal distribution means for distributing the received signal to the fifth and sixth input / output terminals, and the third signal input means or the sixth input / output terminal. Amplitude and phase adjusting means for adjusting the amplitude and phase of the signal distributed by the second signal distributing means, from the first input / output terminal to the fourth input / output terminal through the second and fifth input / output terminals. In the amplitude phase adjustment means, the coupling phase of the first signal path to the second signal path from the first input / output terminal to the fourth input / output terminal through the amplitude phase adjustment means is opposite in phase. The phase adjustment amount is set.

According to the present invention, since the phase adjustment amount in the amplitude phase adjustment means is set so that the coupling phase of the first signal path and the second signal path is opposite, the frequency used Even when the coupling phase changes greatly within the band, there is an effect that the coupling can be reduced over the entire use frequency band.

It is a block diagram which shows the decoupling circuit by Embodiment 1 of this invention. It is a block diagram which shows the amplitude phase adjustment circuit 5 of the decoupling circuit by Embodiment 1 of this invention. It is explanatory drawing which shows an example of the frequency characteristic (characteristic of a single antenna) of the coupling amplitude between the input / output terminal 11 and the input / output terminal 21 when the high-frequency signal passes through the A route. It is explanatory drawing which shows an example of the frequency characteristic (characteristic of a single antenna) of the coupling phase between the input / output terminal 11 and the input / output terminal 21 when the high-frequency signal passes through the A route. It is explanatory drawing which shows an example of the passage characteristic of the parallel resonant circuit 32 connected to the shunt with respect to the transmission line 31. FIG. It is explanatory drawing which shows an example of the passage phase characteristic (phi) _LPF (f) when the parallel resonant circuit 32 is connected to the transmission line 31 by the shunt. Passing through the amplitude and phase adjustment circuit 5 when the parallel resonant circuit 32 having the characteristics shown in FIG. 5 is connected to the shunt with respect to the transmission line 31 having an electrical length of 444 ° at the maximum frequency f _Amax within the used frequency band. It is explanatory drawing which shows phase characteristic (phi) _p (f). FIG. 6 is an explanatory diagram showing the effect of the decoupling circuit according to the first embodiment. It is a block diagram which shows the amplitude phase adjustment circuit 5 of the decoupling circuit by Embodiment 1 of this invention. It is a block diagram which shows the decoupling circuit by Embodiment 2 of this invention. It is a block diagram which shows the amplitude phase adjustment circuit 5 of the decoupling circuit by Embodiment 4 of this invention. It is a block diagram which shows the amplitude phase adjustment circuit 5 of the decoupling circuit by Embodiment 5 of this invention. It is a block diagram which shows the amplitude phase adjustment circuit 5 of the decoupling circuit by Embodiment 6 of this invention.

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
1 is a block diagram showing a decoupling circuit according to Embodiment 1 of the present invention.
In FIG. 1, a distribution circuit 1 serving as a first signal distribution unit includes an input / output terminal 11 (first input / output terminal) for high-frequency signals, an input / output terminal 12 (second input / output terminal) serving as a connection point, and Connected to the input / output terminal 13 (third input / output terminal), the high frequency signal input from the input / output terminal 11 is divided into two, and one high frequency signal after distribution is output to the input / output terminal 12, The other high-frequency signal after distribution is output to the input / output terminal 13. An antenna 3 (first antenna) is connected to the input / output terminal 12.

The distribution circuit 2 as the second signal distribution means includes an input / output terminal 21 (fourth input / output terminal) for high-frequency signals, an input / output terminal 22 (fifth input / output terminal) as connection points, and an input / output terminal 23. (Sixth input / output terminal), the high frequency signal input from the input / output terminal 21 is divided into two, the one high frequency signal after distribution is output to the input / output terminal 22, and the other after distribution Is output to the input / output terminal 23. An antenna 4 (second antenna) is connected to the input / output terminal 22.
The amplitude / phase adjustment circuit 5 is connected between the input / output terminal 13 and the input / output terminal 23, and performs processing for adjusting the amplitude and phase of the high-frequency signal distributed by the distribution circuit 1 or the distribution circuit 2. The amplitude phase adjustment circuit 5 constitutes an amplitude phase adjustment means.

In the first embodiment, the signal path (first signal) of the input / output terminal 11 to the distribution circuit 1 to the input / output terminal 12 to the antenna 3 to the space to the antenna 4 to the input / output terminal 22 to the distribution circuit 2 to the input / output terminal 21. Route) is referred to as A route, and the signal path (second signal path) of the input / output terminal 11 to the distribution circuit 1 to the input / output terminal 13 to the amplitude / phase adjustment circuit 5 to the input / output terminal 22 to the distribution circuit 2 to the input / output terminal 21 ) Is called the B route.
At this time, the signal distribution ratio in the

distribution circuits

1 and 2 and the amplitude adjustment amount in the amplitude phase adjustment circuit 5 are set so that the combined amplitudes of the A route and the B route are equal, and the A route and the B route. The phase adjustment amount in the amplitude and phase adjustment circuit 5 is set so that the coupling phase with the phase is reversed.

FIG. 2 is a block diagram showing an amplitude phase adjustment circuit 5 of the decoupling circuit according to the first embodiment of the present invention.
In FIG. 2, the amplitude / phase adjustment circuit 5 includes a transmission line 31 and a parallel resonant circuit 32 connected to the transmission line 31 in a shunt, and one end of the transmission line 31 is connected to the input / output terminal 13. The other end is connected to the input / output terminal 23.
The parallel resonance circuit 32 includes a capacitor 32a and an inductor 32b, which are lumped constant elements.

Next, the operation will be described.
When a high frequency signal is input from the input / output terminal 11, the distribution circuit 1 distributes the high frequency signal into two, outputs one high frequency signal after distribution to the input / output terminal 12, and outputs the other high frequency signal after distribution. Is output to the input / output terminal 13.
The high frequency signal output from the distribution circuit 1 to the input / output terminal 12 is supplied to the antenna 3, and electromagnetic waves generated by the high frequency signal are radiated from the antenna 3 to the space.
At this time, a part of the electromagnetic wave radiated from the antenna 3 to the space is received by the antenna 4, and a high-frequency signal related to the electromagnetic wave is input to the distribution circuit 2 via the input / output terminal 22.

The high frequency signal output from the distribution circuit 1 to the input / output terminal 13 passes through the amplitude / phase adjustment circuit 5 and is input to the distribution circuit 2 via the input / output terminal 23.
The distribution circuit 2 has a high frequency signal (high frequency signal passing through the A route) input from the antenna 4 via the input / output terminal 22 and a high frequency signal (B) input from the amplitude / phase adjustment circuit 5 via the input / output terminal 23. High-frequency signal passing through the route) and the combined high-frequency signal is output to the input / output terminal 21.

FIG. 3 is an explanatory diagram showing an example of frequency characteristics of the coupling amplitude between the input / output terminal 11 and the input / output terminal 21 when the high-frequency signal passes through the A route (characteristics of the antenna alone).
FIG. 4 is an explanatory diagram showing an example of the frequency characteristic of the coupling phase between the input / output terminal 11 and the input / output terminal 21 when the high-frequency signal passes through the A route (characteristic of the antenna alone).
The coupling of the A route varies depending on the characteristics of the antennas 3 and 4, the arrangement, and the surrounding space conditions.
Here, the combination _{A A} (f) of the A route is defined as the following formula (1).
S _A (f) = s _A (f) exp (jφ _A (f)) (1)
In Equation (1), f is the frequency, s _A (f) is the amplitude of coupling at the frequency f of the A route, and φ _A (f) is the phase of coupling at the frequency f of the A route.
J is an imaginary unit, and j ² = −1. The unit of phase is (°).

On the other hand, the coupling of the B route varies depending on the design value of the amplitude / phase adjustment circuit 5.
Here, the combination S _B (f) of the B route is defined as the following equation (2).
S _B (f) = s _B (f) exp (jφ _B (f)) (2)
In equation (2), f is the frequency, s _B (f) is the amplitude of coupling at the frequency f of the B route, and φ _B (f) is the phase of coupling at the frequency f of the B route.

Here, when the amplitude phase adjustment circuit 5 is designed so that the coupling of the B route has the same amplitude opposite phase as the coupling of the A route over the entire use frequency band, the following expression (3) is given. Such a relationship is established.
S _B (f) = s _B (f) exp (jφ _B (f))
= S _A (f) exp (j (φ _A (f) −180 °)) (3)
Therefore, when the amplitude / phase adjustment circuit 5 is designed as described above, the combination of the A route coupling S _A (f) and the B route coupling S _B (f) is synthesized in the distribution circuit 2 as follows: As shown in 4), the synthesis result is zero.
S _A (f) + S _B (f)
= S _A (f) {exp (jφ _A (f)) + exp (j (φ _A (f) −180 °))}
= 0 (4)

This result indicates that the coupling between the input / output terminal 11 and the input / output terminal 21 is zero.
Therefore, when the amplitude phase adjustment circuit 5 is designed so that the coupling of the B route has the same amplitude opposite phase as that of the coupling of the A route over the entire use frequency band, the input / output terminal 11 and the input / output terminal 21. The coupling between them can be reduced to almost zero.

FIG. 2 shows a configuration example of the amplitude / phase adjustment circuit 5, but it is known that the parallel resonance circuit 32 connected to the transmission line 31 in a shunt acts as a band-pass filter.
When the capacitance of the capacitor 32a of the parallel resonance circuit 32 is Cp (F) and the inductance of the inductor 32b is Lp (H), the relationship between the resonance frequency fr of the parallel resonance circuit 32 and Cp, Lp is expressed by the following equation (5). It is expressed as
Lp = 1 / ((2 × fr × π) ² Cp) (5)
Further, the Q value representing the sharpness of resonance is represented by the following equation (6), where R is the characteristic impedance of the transmission line 31.
Q = R / (2 × π × fr × Lp) = 2 × π × fr × Cp × R (6)

The coupling of the A route via the antennas 3 and 4 and the space generally has bandpass characteristics. Therefore, if the resonant frequency fr and Q value of the parallel resonant circuit 32 are appropriately set, the coupling of the A route S _A (f ) And the B route combination S _B (f) can be made substantially the same.
For example, it is conceivable that the resonance frequency fr of the parallel resonance circuit 32 is set to a frequency f _{Amax at} which the coupling _{A A} (f) of the A route becomes maximum within the use frequency band.
It is also conceivable that the resonance frequency fr of the parallel resonance circuit 32 is set to the center frequency of the used frequency band.

The coupling amplitude difference Δs (f) is defined as in the following equation (7), where the upper limit of the use frequency band is f _H and the lower limit is f _L.
Δs (f) = s (fr) −s (f) (7)
In this case, the Q value of the parallel resonance circuit 32 is determined so as to satisfy, for example, Δs _A (f _H ) = Δs _B (f _H ), Δs _A (f _L ) = Δs _B (f _L ). Conceivable.
Further, a method of searching for the Q value at which the change of the pass amplitude characteristic s _LPF (f) of the parallel resonance circuit 32 is closest to s _A (f) can be considered by the least square method or the like.
Of course, the designer may appropriately select the values of Lp and Cp in consideration of other requirements such as the ease of configuration of the parallel resonant circuit 32 and the distribution of s _A (f).

FIG. 5 is an explanatory diagram showing an example of the pass characteristics of the parallel resonant circuit 32 connected to the transmission line 31 in a shunt.
In the example of FIG. 5, the resonance frequency fr of the parallel resonance circuit 32 is made to coincide with the maximum frequency f _Amax within the use frequency band, and the Q value is set to 59.7. The characteristic impedance R of the transmission line 31 is 50Ω.
From FIG. 5, it is confirmed that the way of changing the pass amplitude characteristic s _LPF (f) within the used frequency band is close to the way of changing the coupling _{A A} (f) of the A route shown in FIG. .
However, the absolute value of the pass amplitude characteristic s _LPF (f) and the absolute value of the coupling _{A A} (f) of the A route may be adjusted according to the characteristics of the

distribution circuits

1 and 2. Only the way of change needs to be matched.
The passing phase characteristic φ _LPF (f) when the parallel resonant circuit 32 is connected to the transmission line 31 in a shunt is as shown in FIG.

Next, a method for determining the distribution ratio of high-frequency signals in the distribution circuit 1 and the distribution circuit 2 will be described.
Here, in the distribution circuit 1, the passing amplitude from the input / output terminal 11 to the input / output terminal 13 is P ₁ (dB), and the passing amplitude from the input / output terminal 11 to the input / output terminal 12 is P ₂ (dB).
In the distribution circuit 2, let the passing amplitude from the input / output terminal 21 to the input / output terminal 23 be P ₁ (dB), and let the passing amplitude from the input / output terminal 21 to the input / output terminal 22 be P ₂ (dB).
Note that the pass characteristics between the terminals in the

distribution circuits

1 and 2 are symmetrical. For example, the pass amplitude from the input / output terminal 13 to the input / output terminal 11 is also P ₁ (dB). The passing amplitude to the output terminal 21 is also P ₁ (dB).

To substantially the same amplitude coupling S _{B (f)} of the coupling S _{A (f)} and B routes A route throughout the frequency band, for example, to satisfy the equation (8) (9) below Thus, it is conceivable to determine the distribution ratio.

The B route coupling S _B (f) is determined from the distribution ratio of the

distribution circuits

1 and 2 and the pass amplitude characteristics of the parallel resonant circuit 32 connected to the transmission line 31 in a shunt.

To match the throughout the frequency band A route combined phase phi _{A (f)} and B routes combined phase phi _{B (f)} is over the entire frequency band, the following equation (10 The amplitude / phase adjustment circuit 5 must be designed so as to satisfy (2).
φ _B (f) = φ _A (f) −180 ° (10)

Hereinafter, in distribution circuit 1, φ _11-13 (f), which is a passing phase characteristic from input / output terminal 11 to input / output terminal 13, is 0, and in distribution circuit 2, input / output terminal 23 is connected to input / output terminal 21. The description will be made assuming that φ _23-21 (f), which is the passing phase characteristic, is 0, but the same can be considered when these have values.
When the passing phase characteristics φ _11-13 (f) and φ _23-21 (f) are 0, the passing phase characteristics φ _p (f) of the amplitude phase adjusting circuit 5 and the B phase combined phase φ _B (f) Therefore, the amplitude phase adjustment circuit 5 may be designed so as to satisfy the following expression (11).
φ _p (f) = φ _B (f) = φ _A (f) + 180 ° (11)

Next, an example of a method for determining the electrical length θ of the transmission line 31 at the maximum frequency f _Amax within the use frequency band will be described.
The electrical length θ of the transmission line 31 is set so as to satisfy the following conditions (1) and (2).
(1) at the maximum frequency _{f Amax} in the used frequency band, A route combined phase phi _A and _{(f Amax),} combined phase phi _B of Route B _{(f Amax)} is substantially opposite phase.
(2) Δφ _A = φ _A (f _L ) −φ _A (f _H ) is substantially equal to Δφ _B = φ _B (f _L ) −φ _B (f _H ).
Therefore, the electrical length θ of the transmission line 31 that satisfies the above conditions (1) and (2) can be determined from the following equation (12).

In equation (12),
Δφ _LPF = − (φ _LPF (f _H ) −φ _LPF (f _L ))

FIG. 7 shows an amplitude and phase adjustment circuit when a parallel resonant circuit 32 having the characteristics shown in FIG. 5 is connected to a shunt with respect to a transmission line 31 having an electrical length of 444 ° at the maximum frequency f _Amax within the used frequency band. FIG. 5 is an explanatory diagram showing a pass phase characteristic φ _p (f) of FIG.
Compared with the combined phase φ _A (f) of the A route shown in FIG. 4, the passing phase characteristic φ _p (f) of the amplitude phase adjustment circuit 5 has a phase of almost 180 ° over the entire use frequency band. You can see that they are different.

By combining the distribution circuit 1, the distribution circuit 2, and the amplitude phase adjustment circuit 5 designed as described above, the coupling between the input / output terminal 11 and the input / output terminal 21 can be reduced within the used frequency band.
FIG. 8 is an explanatory diagram showing the effect of the decoupling circuit according to the first embodiment.
In FIG. 8, the characteristics of the single antenna shown in FIG. 3 are also described.
By applying the present invention, the worst value of the coupling between the input and output terminals within the used frequency band is about −20 dB (1/100) compared to the case without the decoupling circuit. The effect of the present invention to reduce the coupling over the entire use frequency band is confirmed.

As apparent from the above, according to the first embodiment, the signal distribution ratio in the

distribution circuits

1 and 2 and the amplitude adjustment amount in the amplitude phase adjustment circuit 5 are set so that the coupling amplitudes of the A route and the B route become equal. Is set, and the phase adjustment amount in the amplitude phase adjustment circuit 5 is set so that the coupling phase of the A route and the B route is opposite to each other. Even when the coupling amplitude and the coupling phase change greatly, the coupling between the input / output terminal 11 and the input / output terminal 21 can be reduced over the entire use frequency band.
It is not particularly difficult to manufacture all of the

distribution circuits

1 and 2 and the amplitude / phase adjustment circuit 5 on the same substrate. In addition, since the amplitude phase adjustment circuit 5 is mounted with a resonance circuit and the change in the passing amplitude and the passing phase difference becomes large, the circuit can be miniaturized.

In the first embodiment, the amplitude phase adjustment circuit 5 in which one parallel resonance circuit is connected to the transmission line 31 in a shunt is shown, but the amplitude adjustment amount and the phase adjustment amount in the amplitude phase adjustment circuit 5 are appropriately designed. If so, the amplitude / phase adjustment circuit 5 may have another configuration.
For example, in order to configure the amplitude phase adjustment circuit 5 in which the change of the passing amplitude and the phase difference is extremely steep, a resonance circuit having an extremely high Q value is required. Although it is difficult to realize a resonance circuit having an extremely high Q value, an amplitude / phase adjustment circuit 5 having similar pass characteristics can be configured by combining a plurality of resonance circuits.

Further, as another configuration of the amplitude phase adjustment circuit 5, as shown in FIG. 9, an amplitude phase adjustment circuit 5 in which a series resonance circuit 35 is connected in series to the

transmission lines

33 and 34 may be used.
In the example of FIG. 9, the series resonance circuit 35 is configured by connecting an inductor 35a and a capacitor 35b in series.
Even when the amplitude / phase adjusting circuit 5 is configured as shown in FIG. 9, if the resonance frequency and Q value of the series resonance circuit 35 are set appropriately, the A route coupling S _A (f) and the B route coupling S _B ( f) can be made substantially identical.

When the inductance of the inductor 35a of the series resonance circuit 35 is Ls (H) and the capacitance of the capacitor 35b is Cs (F), the relationship between the resonance frequency fr of the series resonance circuit 35 and Cs, Ls is expressed by the following equation (13). It is expressed as
Ls = 1 / ((2 × fr × π) ² Cs) (13)
Further, the Q value representing the sharpness of resonance is represented by the following equation (14), where R is the characteristic impedance of the

transmission lines

33 and 34.
Q = (2 × π × fr × Ls) / R = 1 / (2 × π × fr × Cs × R)
(14)
The amplitude / phase adjustment circuit 5 may include both the parallel resonance circuit 32 and the series resonance circuit 35.

Embodiment 2. FIG.
10 is a block diagram showing a decoupling circuit according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG.
A directional coupler 6 (first directional coupler) which is a first signal distribution means is connected to the input / output terminal 11, the input / output terminal 12, the input / output terminal 13 and the input / output terminal 14. The high-frequency signal input from the terminal 11 is divided into two, one high-frequency signal after distribution is output to the input / output terminal 12, and the other high-frequency signal after distribution is output to the input-output terminal 13. The input / output terminal 14 is connected to the GND conductor 43 via a termination resistor 41.
The directional coupler 7 (second directional coupler) as the second signal distribution means is connected to the input / output terminal 21, the input / output terminal 22, the input / output terminal 23, and the input / output terminal 24. The high-frequency signal input from the terminal 21 is divided into two, one high-frequency signal after distribution is output to the input / output terminal 22, and the other high-frequency signal after distribution is output to the input-output terminal 23. The input / output terminal 24 is connected to the GND conductor 43 via a termination resistor 42.

In the first embodiment, the

distribution circuits

1 and 2 distribute the high-frequency signal input from the input /

output terminals

11 and 21 and output one of the distributed high-frequency signals to the input /

output terminals

12 and 22 for distribution. The other high-frequency signal is output to the input /

output terminals

13 and 23. As shown in FIG. 10, the directional couplers 6 and 7 receive the high-frequency signal input from the input /

output terminals

11 and 21, respectively. Alternatively, the divided high frequency signal may be output to the input /

output terminals

12 and 22, and the other high frequency signal after distribution may be output to the input /

output terminals

13 and 23.

In the directional coupler 6, the coupling amount between the input / output terminal 11 and the input / output terminal 14 is very small, and the coupling amount between the input / output terminal 12 and the input / output terminal 13 is very small.
In the directional coupler 7, the coupling amount between the input / output terminal 21 and the input / output terminal 24 is very small, and the coupling amount between the input / output terminal 22 and the input / output terminal 23 is very small.
Therefore, in the directional coupler 6, isolation between the input / output terminal 12 and the input / output terminal 13 is ensured, and in the directional coupler 7, isolation between the input / output terminal 22 and the input / output terminal 23 is ensured. Therefore, the distribution ratio and the like can be easily designed by the same method as the

distribution circuits

1 and 2.
The resistance values of the

termination resistors

41 and 42 are generally the same as the standardized impedance for designing the directional couplers 6 and 7 (for example, 50Ω), but the resistance values are not limited to this. .

According to the second embodiment, as in the first embodiment, even when the coupling amplitude and the coupling phase between the antennas greatly change within the use frequency band, the input / output terminals over the entire use frequency band. 11 and the input / output terminal 21 can be reduced. In addition, it is possible to obtain a decoupling circuit that is easy to design.

Embodiment 3 FIG.
In the first embodiment, the Q value of the parallel resonant circuit 32 is set so that the coupling S _A (f) of the A route matches the coupling S _B (f) of the B route. The Q value of the parallel resonance circuit 32 may be set so that the passing phase characteristic φ _p (f) of the amplitude phase adjustment circuit 5 is equal to the coupling phase φ _A (f) of the A route.
When the Q value of the parallel resonant circuit 32 is set to be φ _A (f) = φ _p (f), the electrical length θ (f) of the transmission line 31 is determined by the following equation (15), for example. Is done. However, in Formula (15), φ _A (fr) + 180 ° and φ _B (fr) are matched, but the reference frequency is not limited to the resonance frequency fr.
φ _B (fr) = θ (fr) = φ _A (fr) + 180 ° (15)
Since the range of φ _A (f) is [−180 °, 180 °], the range of θ (f) is [0 °, 360 °].

As described above, the Q value of the parallel resonance circuit 32 is set so that the passing phase characteristic φ _p (f) of the amplitude phase adjustment circuit 5 is equal to the coupling phase φ _A (f) of the A route. The electrical length θ (f) of the transmission line 31 can be 360 ° at the maximum.
As a result, it is possible to reduce the coupling between the antennas over a wide band and to obtain an effect of obtaining a small decoupling circuit.

Embodiment 4 FIG.
FIG. 11 is a block diagram showing an amplitude / phase adjustment circuit 5 of a decoupling circuit according to Embodiment 4 of the present invention. In the figure, the same reference numerals as those in FIG.
The short stub 36 is a distributed constant line connected to the transmission line 31 in a shunt, and realizes a parallel resonance circuit for the transmission line 31.
In the fourth embodiment, it is assumed that the short stub 36 is realized by a triplate line formed in the inner layer of the multilayer substrate. However, the method of manufacturing the short stub 36 is not limited to this. For example, it may be realized by a microstrip line on a substrate.

In the first embodiment, the Q value of the parallel resonance circuit 32 is set so that the coupling S _A (f) of the A route matches the coupling S _B (f) of the B route. Depending on the Q value of 32, it may be difficult to realize the element values of the capacitor 32a and the inductor 32b. In such a case, the parallel resonant circuit 32 is formed by the capacitor 32a and the inductor 32b which are lumped elements. It is expected to be difficult to construct.
On the other hand, it is known that a stub structure constituted by distributed constant lines can be used as a resonance circuit.

Therefore, in the fourth embodiment, the amplitude / phase adjusting circuit 5 is configured by connecting the short stub 36 to the shunt with respect to the transmission line 31.
As shown in FIG. 11, the short stub 36 serves as a parallel resonant circuit, so that the Q value can be freely determined without being restricted by the value of the lumped element.
Therefore, effects that can be matched coupling S _A of Route A a _(f) and B root of binding S _{B (f)} more precisely can be obtained.

As described above, the method for producing the short stub 36 is not particularly limited. However, when realized with a triplate line, the characteristic impedance of the stub can be lowered as compared with the case of realizing with a microstrip line. The parallel resonant circuit can be made.
In addition, if a multilayer substrate is used, a plurality of stubs can be arranged in an overlapping manner, so that the circuit area can be reduced.

In the example of FIG. 11, the short stub 36 is connected to the shunt with respect to the transmission line 31, but an open stub may be used instead of the short stub 36.
When a plurality of resonance circuits are used, some or all of the resonance circuits may be realized by stubs.
In the fourth embodiment, the stub structure constituted by the distributed constant line is used as the parallel resonant circuit 32. However, the stub structure constituted by the distributed constant line is used as the series resonant circuit 35. It may be.

Embodiment 5 FIG.
FIG. 12 is a block diagram showing the amplitude phase adjustment circuit 5 of the decoupling circuit according to the fifth embodiment of the present invention. In the figure, the same reference numerals as those in FIG.
The meander line 37 is a transmission line having one end connected to the input / output terminal 13 and the other end connected to the input / output terminal 23.

In the first embodiment, the input / output terminal 13 and the input / output terminal 23 are connected by the transmission line 31. However, the transmission line 31 is configured by a meander line 37 as shown in FIG. May be.
By configuring the transmission line 31 with the meander line 37, the transmission line can be downsized.

Here, an example is shown in which the transmission line 31 in the amplitude / phase adjustment circuit 5 of FIG. 2 is configured by the meander line 37, but the

transmission lines

33 and 34 in the amplitude / phase adjustment circuit 5 of FIG. 9 are configured by the meander line 37. Alternatively, the transmission line 31 in the amplitude / phase adjustment circuit 5 of FIG. 11 may be configured by the meander line 37.

Embodiment 6 FIG.
FIG. 13 is a block diagram showing the amplitude phase adjustment circuit 5 of the decoupling circuit according to the sixth embodiment of the present invention. In the figure, the same reference numerals as those in FIG.
In the example of FIG. 13, a plurality of lumped constant elements 51 (for example, capacitors and inductors) connected in series and a plurality of lumped constant elements 52 (for example, capacitors and inductors) connected to the lumped constant elements 51 and the shunt are used. ) To form a T-type phase shift circuit, and a plurality of phase shift circuits carry transmission lines.
Thus, the amount of phase shift can be increased by combining a plurality of phase shift circuits.
In FIG. 13, since the phase shift circuit is configured only by the lumped

constant elements

51 and 52, the circuit can be reduced in size.
Further, although a T-type phase shift circuit is shown in FIG. 13, it may be a saddle type phase shift circuit.

In the first to sixth embodiments, the antennas 4 and 5 are connected to the input /

output terminals

12 and 22, and the example in which the coupling between the antennas is reduced has been described. When the coupling exists between the input / output terminal 11 and the input / output terminal 21 through some propagation medium, the coupling can be reduced by applying the present invention.

In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

The decoupling circuit according to the present invention is suitable, for example, for a circuit that has a high need for enabling sufficient effects of diversity and MIMO by reducing the coupling between two antennas.

1 distribution circuit (first signal distribution means), 2 distribution circuit (second signal distribution means), 3 antenna (first antenna), 4 antenna (second antenna), 5 amplitude phase adjustment circuit (amplitude phase) Adjustment means), 6 directional coupler (first directional coupler, first signal distribution means), 7 directional coupler (second directional coupler, second signal distribution means), 11 input Output terminal (first input / output terminal), 12 Input / output terminal (second input / output terminal), 13 Input / output terminal (third input / output terminal), 14 Input / output terminal, 21 Input / output terminal (fourth Input / output terminal), 22 input / output terminal (fifth input / output terminal), 23 input / output terminal (sixth input / output terminal), 24 input / output terminal, 31 transmission line, 32 parallel resonant circuit, 32a capacitor,

32b inductor

33, 34 Transmission line, 35 Series resonant circuit, 35a inductors, 35b capacitor 36 short stub, 37 meander line, 41 terminating resistor, 43 GND conductor, 51, 52 lumped element.

Claims

First signal distribution means for distributing a signal input from the first input / output terminal to the second and third input / output terminals;
Second signal distribution means for distributing a signal input from the fourth input / output terminal to the fifth and sixth input / output terminals;
An amplitude which is connected between the third input / output terminal and the sixth input / output terminal and adjusts the amplitude and phase of the signal distributed by the first signal distribution means or the second signal distribution means. Phase adjustment means,
A first signal path from the first input / output terminal through the second and fifth input / output terminals to the fourth input / output terminal; and from the first input / output terminal through the amplitude phase adjusting means. The decoupling circuit, wherein the phase adjustment amount in the amplitude phase adjusting means is set so that the coupling phase with the second signal path leading to the fourth input / output terminal is opposite in phase.
The signal distribution ratio in the first and second signal distribution means and the amplitude adjustment amount in the amplitude phase adjustment means are set so that the coupling amplitudes of the first signal path and the second signal path are equal. The decoupling circuit according to claim 1, wherein:
The first signal distribution means distributes a signal input from the first input / output terminal into two, outputs one signal after distribution to the second input / output terminal, and outputs the other signal after distribution to the other A distribution circuit for outputting a signal to the third input / output terminal;
The second signal distribution means distributes the signal input from the fourth input / output terminal into two, outputs one signal after distribution to the fifth input / output terminal, and outputs the other signal after distribution to the other 2. The decoupling circuit according to claim 1, comprising a distribution circuit that outputs a signal to the sixth input / output terminal.
The first signal distribution means distributes a signal input from the first input / output terminal into two, outputs one signal after distribution to the second input / output terminal, and outputs the other signal after distribution to the other A first directional coupler for outputting a signal to the third input / output terminal;
The second signal distribution means distributes the signal input from the fourth input / output terminal into two, outputs one signal after distribution to the fifth input / output terminal, and outputs the other signal after distribution to the other A second directional coupler that outputs a signal to the sixth input / output terminal;
2. The decoupling circuit according to claim 1, wherein a terminal that does not output a signal in the first and second directional couplers is grounded.
The amplitude phase adjusting means is composed of a resonance circuit and a transmission line,
The Q value of the resonant circuit is set so that the coupling amplitudes of the first signal path and the second signal path are equal;
3. The decoupling circuit according to claim 2, wherein the length of the transmission line is set so that a coupling phase between the first signal path and the second signal path is opposite.
The resonant circuit is a parallel resonant circuit connected in a shunt with respect to the transmission line or a series resonant circuit connected in series with the transmission line, and the parallel resonant circuit or the series resonant circuit is configured by a lumped element. 6. The decoupling circuit according to claim 5, wherein the decoupling circuit is provided.
The resonant circuit is a parallel resonant circuit connected in a shunt with respect to the transmission line or a series resonant circuit connected in series with the transmission line, and the parallel resonant circuit or the series resonant circuit is configured by a distributed constant line 6. The decoupling circuit according to claim 5, wherein the decoupling circuit is provided.
8. The decoupling circuit according to claim 7, wherein the distributed constant line is composed of a stub made of a triplate line.
6. The decoupling circuit according to claim 5, wherein the transmission line is formed of a meander line.
6. The decoupling circuit according to claim 5, wherein the transmission line is composed of a T-type or saddle-type phase shift circuit composed of lumped constant elements.
A first antenna is connected to the second input / output terminal,
The decoupling circuit according to claim 1, wherein a second antenna is connected to the fifth input / output terminal.